High temporal and spatial coherence of laser illumination may result in unwanted artifacts and errors in a detected signal. For example, pixel edges, coating blemishes, or specks of dust on a lens in a coherent optical system may produce diffraction patterns on an illuminated object, modulating or sometimes even obscuring a desired illumination pattern and thereby producing detected signal errors, herein referred to as diffraction artifacts. Moreover, microscopic roughness on the illuminated object may produce a diffraction pattern of its own leading to spatial intensity fluctuations at the detector, herein referred to as speckle. Speckle may occur at the focal plane of an imaging lens or in free space in the near or far field of the illuminated object, and may be a dominant source of error in a laser-based illumination and detection system. Speckle and diffraction artifacts may affect image quality as well as measurement resolution and accuracy in laser-based structured-illumination three-dimensional (3D) sensing of object surfaces, in structured illumination microscopy, and in other imaging systems employing laser pattern projection, for example. There is thus a need for tools and techniques that may enable suppression of speckle and/or diffraction artifacts in coherent structured illumination sensing systems.